Modulation transfer spectroscopy based on acousto-optic modulator with zero frequency shift<xref rid="cpb_27_11_114203fn1" ref-type="fn">*</xref> <fn id="cpb_27_11_114203fn1"> <label>*</label> <p>Project supported by the National Key Research and Development Program of China (Grant No. 2016YFA0302101), the Foundation of China Academy of Space Technology, and the Initiative Program of State Key Laboratory of Precision Measurement Technology and Instruments, China.</p> </fn>

Modulation transfer spectroscopy based on acousto-optic modulator with zero frequency shift* *

Project supported by the National Key Research and Development Program of China (Grant No. 2016YFA0302101), the Foundation of China Academy of Space Technology, and the Initiative Program of State Key Laboratory of Precision Measurement Technology and Instruments, China.

Wu Chen-Fei^{1, 2}, Yan Xue-Shu^{2, 3}, Wei Li-Xun⁴, Ma Pei⁴, Tu Jian-Hui⁴, Zhang Jian-Wei^{2, 3, †}, Wang Li-Jun^{1, 2, 3, ‡}

(color online) (a) Schematic diagram of alternative double pass structure for frequency shift cancellation. The laser beam is focused on acousto-optic crystal; then, after positive first-order diffraction, it is collimated by using lens and reflected back symmetrically via right-angled prism; negative first-order shift then occurs in the second pass, and zero frequency shift is obtained. f: focal length of lens; AOM: acousto-optic modulator; PBS: polarizing beam splitter; λ/2: half-wave plate; RAP: right-angled prism. (b) Schematic of MTS system based on AOM with no frequency shift. A pump laser beam is modulated by using AOM and this modulation is transferred to probe beam within cesium cell. Saturation absorption spectrum (SAS) and demodulated MTS signals are monitored simultaneously on an oscilloscope. A feedback loop is used for laser frequency locking. PD: photo-detector; A: amplifier; LPF, low-pass filter.